ꢀ ꢁꢂ ꢂ ꢃ ꢄ ꢂꢅ ꢆ ꢀ ꢁꢂ ꢇꢃ ꢄꢂ ꢅ
ꢈ ꢉ ꢊ ꢋꢅ ꢌ ꢍꢅ ꢎ ꢏꢐ ꢐ ꢑꢒ ꢓꢏꢔ ꢁꢎꢓ ꢕꢖꢗ ꢍꢘꢒ ꢕꢖ ꢙ ꢑꢚ ꢕ ꢒꢁ ꢛꢕꢖ ꢙ ꢘꢍꢙ ꢔ ꢜꢅꢒꢐ ꢘꢑ
SLLS636D – DECEMBER 2004 – REVISED MARCH 2005
TYPICAL CHARACTERISTICS
1
8
Q2
S
R
Q
Q1
2
7
6
1N5819
I
R
pk
SC
0.33 Ω
C
T
Oscillator
3
V
in
25 V
V
CC
L
C
T
220 µH
1.25-V
Reference
Regulator
470 pF
+
+
_
100 µF
Comparator
4
5
1.0 µH
100 µF
R2
3.8 kΩ
V
out
5 V/500 mA
V
out
+
+
R1
1.2 kΩ
C
O
470 µF
Optional Filter
RESULTS
TEST
CONDITIONS
= 15 V to 25 V, I = 500 mA
Line Regulation
Load Regulation
Output Ripple
V
IN
V
IN
V
IN
V
IN
V
IN
V
IN
12 mV 0.12%
3 mV 0.03%
O
= 25 V, I = 50 mA to 500 mA
O
= 25 V, I = 500 mA
120 mV
1.1 A
O
PP
Short-Circuit Current
Efficiency
= 25 V, R = 0.1 Ω
L
= 25 V, I = 500 mA
83.7%
O
Output Ripple With Optional Filter
= 25 V, I = 500 mA
40 mV
PP
O
Figure 8. Step-Down Converter
7
POST OFFICE BOX 655303 • DALLAS, TEXAS 75265
TI [ TEXAS INSTRUMENTS ]
